Evolved Multimedia Broadcast Multicast Services (eMBMS) have been offered over Universal Terrestrial Radio Access Network (UTRAN) and Long-Term Evolution (LTE) wireless communication standards. eMBMS enables broadcast over multiple cells via a single-frequency network (SFN) and are proposed, in the 3rd Generation Partnership Project (3GPP) Group Communication System Enablers (GCSE) for LTE standards, to be used for public safety applications, including mission critical push-to talk, voice and video.
A header compression mechanism is defined in the 3GPP standards for eMBMS over UTRAN, but as of release 12 of 3GPP specifications, is not defined in the 3GPP standards for eMBMS over LTE.
One reason that header compression is not enabled for eMBMS over LTE is that when a receiver enters a Multicast-Broadcast Single-Frequency Network (MBSFN) area after a transmission starts (e.g., concerning a “late joiner”), the receiver will miss the first control packets that carry header compression synchronization information.
Header compression methods typically used for eMBMS over UTRAN, such as Unidirectional Mode Robust Header Compression (ROHC-U described in RFC 3095), do not include full headers in the packets until the header compression is re-synchronized. Therefore, a late joiner cannot rebuild or de-compress the subsequent packets.
Further, if no header compression is used for eMBMS over LTE, uncompressed headers accompany every packet and can be very large relative to the size of the payload. For example, headers typically used for eMBMS, such as Real-time Transport Protocol (RTP) headers, User Datagram Protocol (UDP) headers or Internet Protocol (IP) headers, can use approximately 48 bytes per packet. Therefore, without header compression, eMBMS over LTE can be very wasteful of downlink over-the-air bandwidth.
Accordingly, there is a need for an improved method and system for data transmission.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.